Injector with minimal flow-interrupt transient

Abstract

An injector is described for injecting a sample at a high pressure into a chromatographic column, which avoids sample dilution that is characteristic of bypass loop injectors, and which also avoids significant flow interruption into the column that is characteristic of prior non-bypass injectors. The stator includes pump and column ports with openings (34a, 42a, FIG. 4) at the stator-rotor interface, where the openings are spaced by a small angle (m) of less than 10° from one another. In the load position, a channel (50) formed in the interface surface of the rotor, which connects the pump and column openings in the load position, extends away from the pump opening by an angle (n) which is many times greater than the angle between the pump and column openings. As a result, as the injector is turned toward the inject position, the channel (50) continues to connect the pump and column openings until the rotor is close to the inject position. As the inject position is approached (FIG. 8), the trailing edge (50t) of the channel passes beyond the pump openings (34 a), while the leading edge (50f) of the channel connects to a sample opening (the channel is always connected to the column opening (42a). Thus, when the rotor is rapidly turned from load to inject positions, there is only a very brief interruption of liquid flow into the column.

What is claimed is: 
     
       1. In an injector which includes a rotor that can pivot between load and inject positions about an axis and that has a sample-receive port for receiving a sample, and which also includes a stator with pump, column, first-sample, vent, and second-sample ports, and with the rotor having first and second channels at the rotor-stator interface, each channel having leading and trailing edges, the first channel connecting the pump and column ports at the load position and connecting the column and first-sample ports at the inject position, and the second channel connecting the second-sample and vent ports in the load position and coupling the second-sample port to the pump port in the inject position, the improvement wherein: said pump port includes a pump inlet spaced from said stator-rotor interface, first and second spaced pump openings in said stator at the stator-rotor interface, and a conduit in said stator which connects said pump inlet to said first and second pump openings;   said column port has an opening at the stator-rotor interface and said first pump opening has an edge that lies at an angle of less than 10° about said axis from the nearest edge of said column opening, said second pump opening is spaced by more than twice said angle from said first pump opening, and said second channel is positioned so that in the inject position said second channel connects the second-sample opening to said second pump opening; and   said second channel is positioned so that at a transition position at which the trailing edge of the first channel breaks connection with said pump port, during rotor pivoting toward the inject position, the leading edge of the second channel lies within 10° of connection with the pump port.   
     
     
       2. The improvement described in claim 1 wherein: said channels are positioned so that in the load position, said column opening lies at one end of said first channel, said second pump opening lies at the opposite end of said first channel, and said first pump opening lies between them and in connection with said first channel.   
     
     
       3. In an injector which includes a rotor that can pivot between load and inject positions about an axis and that has a sample-receive port for receiving a sample, and which also includes a stator with pump, column, first-sample, vent, and second-sample ports, and with the rotor having first and second channels at the rotor-stator interface, each channel having leading and trailing edges, the first channel connecting the pump and column ports at the load position and connecting the column and first-sample ports at the inject position, and the second channel connecting the second-sample and vent ports in the load position and coupling the second-sample port to the pump port in the inject position, the improvement wherein: said channels are positioned so that at a transition position at which the trailing edge of said first channel breaks connection with said pump port during rotor pivoting toward the inject position, the leading edge of said second channel is already connected to said pump port.   
     
     
       4. The improvement described in claim 3 wherein: said pump port has first and second pump openings at the rotor-stator interface, and said pump openings are spaced apart by more than 10° and are positioned so that at said transition position the trailing edge of said first channel just breaks connection with said first pump opening and the leading edge of said second channel has made connection with only a portion of said second pump port.   
     
     
       5. An injector comprising: stator and rotor elements which can rotate relative to one another angularly about an axis of rotation between predetermined load and inject positions, and which have adjacent interface surfaces;   a first of said elements having a pump port for receiving a mobile phase fluid high pressure, a column port for delivering fluid to a chromatography column, first and second sample ports for connection to opposite ends of a sample loop, and a vent port for venting fluid, each port having at least one opening at the interface between the elements;   a second of said elements having a sample-receive port for receiving a sample fluid, said second element also having first and second largely circumferentially-extending channels in its face;   said openings positioned with the opening of said second-sample port lying angularly between a pump opening and the opening at said vent port, and said second channel positioned so in said load position said second channel extends between said second-sample and vent openings, and in said inject position said second channel extends between said second-sample opening and a pump opening;   said column opening lying angularly between a pump opening and said first-sample opening, and in the load position said first channel extends between a pump opening and said column opening, and in the inject position said first channel extends between said column opening and first-sample opening;   said pump port has two angularly-spaced pump openings at the interface surface of said first element, including a first pump opening positioned so it opens to said first channel and is connected therethrough to said column opening in the load position, but does not open to either channel in the inject position, and a second pump opening positioned so it opens to said second channel and is connected therethrough to said second-sample opening in the inject position.   
     
     
       6. The injector described in claim 5 wherein: said second pump opening is positioned so it lies at an end of said first channel in the load position, and lies at an end of said second channel in the inject position.   
     
     
       7. An injector comprising: stator and rotor elements which can rotate relative to one another angularly about an axis of rotation between predetermined load and inject positions, and which have adjacent interface surfaces;   a first of said elements having a pump port for receiving a mobile phase fluid under high pressure, a column port for delivering fluid to a chromatography column, first and second sample ports for connection to opposite ends of a sample loop, and a vent port for venting fluid, each port having at least one opening at the interface between the elements;   a second of said elements having a sample-receive port for receiving a sample fluid, said second element also having first and second largely circumferentially-extending channels in its face;   said openings positioned with the opening of said second-sample port lying angularly between a pump opening and the opening at said vent port, and said second channel positioned so in said load position said second channel extends between said second-sample and vent openings, and in said inject position said second channel extends between said second-sample opening and a pump opening;   said column opening lying angularly between a pump opening and said first-sample opening, and said first channel is positioned so in the load position said first channel extends between a pump opening and said column opening, and in the inject position said first channel extends between said column opening and first-sample opening;   said channels each have leading and trailing edges, said channels are positioned so that at a predetermined transition position between the load and inject positions, the trailing edge of said first channel and the leading edge of said second channel are each partially connected to the pump port.   
     
     
       8. A method for using an injection device having stator and rotor elements that lie adjacent at an interface, to transfer a sample fluid from a container to an analyzing apparatus such a chromatographic column at high pressure, comprising: placing said rotor element in a load position and loading said device, including pumping said sample fluid at low pressure from said container through a port of a first of said elements to an interface between said elements, through a first-sample port of a second of said elements, through a sample loop, through a second-sample port of said second element to said interface, and through a second channel in said second element;   said step of loading also includes pumping a solvent fluid from a high pressure pump through a pump port of said second element to said interface, through a first channel in said first element and from said first channel to a column port of said first element that is connected to an analyzing apparatus;   turning said rotor element to an inject position and at said inject position pumping said solvent at high pressure from said pump port, through said second channel, through said second-sample port and said loop to said first sample port, and through said first channel to said column port, to said analyzing apparatus;   said pump port has two spaced pump openings at said interface, and said step of turning includes disconnecting a first of said pump openings from said first channel and connecting said second channel to a second of said pump openings, all within 10° of rotation of said rotor.   
     
     
       9. The method described in claim 8 wherein: said step of turning includes at least partially connecting said second channel to said pump port before completely disconnecting said first channel from said pump port.